The present invention relates to imprinting images in transparent media. More particularly it relates to method and apparatus for imprinting color images in transparent medium, and in particular in transparent light-sensitive glass.
Colorless marking of images on or within glass is known. Description of a method and equipment for generating of colorless marks at or underneath glass surface with a laser beam, with energy density generated in its focus point sufficient to form an increased opacity area relative to the visible spectrum part in transparent material, can be found in U.S. Pat. Nos. 4,467,172 and 5,206,496.
In RU Pat. No. 2008288 a description of a technique of generating 3-dimensional patterns in glass, in which the pattern formation while retaining the transparency of the specimen surface is achieved by exceeding the threshold value of the volumetric glass breakdown while simultaneously displacing the specimen with respect to the focused laser beam. However, the patterns generated in the glass using the mentioned methods are colorless and are of low-contrast, which strongly impairs the product consumer""s features and appeal.
Color patterns in porous glasses can be generated using the method described in U.S. Pat. No. 4,403,031, in which the liquid that fills the quartz glass pores and contains organic and metal compounds is colored due to photolytic reaction activated by irradiating it with light whose wavelength is in range between 230 to 400 nm.
According to the method described in European Patent application No. 98940718.4, colored three dimensional (3D) images can be generated in transparent porous glasses by focusing laser radiation of wave length of 1060 nm irradiated on the material contained within the pores, which is capable of irreversible color change under the action the optical breakdown factors and subsequent treatment (chemical, thermal, light or acoustical). In porous glasses light-sensitive components do not constitute a part of their chemical composition, but rather they are added to the substance, filling the pores. Moreover, the light transparency coefficient of these glasses is lower in comparison with normal glasses, because the porous glasses are, in reality, a multiphase substance. As a result the field of application of products with colored patterns in porous glasses is limited.
Alternatively the special features of light-sensitive glasses, including polychromatic glasses can be used to obtain color markings. Light-sensitive glasses include light-sensitive components that are a part of their chemical composition. As a result these glasses gain color under the action of actinic (UV, X-, xcex3-) radiation with subsequent thermal treatment. For example, Stookey (U.S. Pat. No. 4,266,012) suggests a photo-process in which 3-8 colored micro-mosaic filters are designed from different shape polychromatic glass plates or 0.01-1.5 mm films.
In order to make use of the known correlation between light-sensitive glass color and actinic radiation exposure time for generating colored images in such glasses Luers developed a photo-process of generating a black and white negative (U.S. Pat. No. 4,302,235) and semi-transparent net patterns (U.S. Pat. No. 4,295,872).
A color-shaded pattern is obtained by light irradiation on polychromatic glass via a negative or different templates in the wave lengths range of 280 to 320 nm and with total intensity range of 0.4-2.4 Joule/cm2, and subsequent thermal treatment at a temperature between the transformation point (log xcex7=13,4 P) and the glass softening point (logxcex7=7,6 P).
Light-sensitive glasses or their more advances typexe2x80x94polychromatic glasses, which can be colored upon cyclic irradiation of UV radiation and mandatory thermal treatment, contain light-sensitive metals (e.g. Au, Ag) and light-sensitivity sensitizers, such as optical (e.g. CeO2) or thermal ones (e. g. SnO, Sb2O3). Numerous studies were dedicated to the compositions of light-sensitive glasses (e.g. U.S. Pat. Nos. 4,017,328, 4,057,408, 4,092,139, 4,134,747, and 4,328,299). In spite of a great number of known compositions their elaboration is being continued nowadays and is aimed at optimizing light-sensitive glass features needed to obtain the required color shades customized to a variety of purposes and the techniques of generating colored images.
For example, U.S. Pat. No. 5,078,771 describes compositions of polychromatic glasses, which are being synthesized and placed as a 0.1xcexc layer at the surface of glass matrix during the course of ions exchange, taking into consideration the chemical composition of specifically adopted bath. Under the action of high-energy laser beam in the wavelength range of 200-300 nm digital or other visual information can be recorded and later developed by thermal treatment and etching in hydrofluoric acid. Such information carriers in a form of products with surface topography can be applied in electronics and computer technologies.
Description of similar technology of etching of parts made from light-sensitive glass in hydrofluoric acid, which were irradiated with UVxe2x80x94laser pulse radiation and underwent subsequent thermal treatment, can be found in U.S. Pat. No. 5,322,538. Products manufactured using this technology were offered for use in high-quality heads of printing devices.
In the coloring methods described in the above references colored information in light-sensitive glass is generated either in a form of marks (patterns) at the surface or penetrating from the surface to the material depth. Namely, these methods cannot be used for generating color patterns localized in light-sensitive glass volume and not related to the product surface.
Furthermore the methods described in the prior art utilize external UV radiation in order to acquire color images within the sample, and as a result there always exist traces of color going from the surface inwardly.
A main object of the present invention is to provide a method and apparatus for generating colored marks (patterns) localized in the volume of light-sensitive glass but not related to the product surface i.e. there is no contact of colored image with the surface of specimen.
It is therefore thus provided, in accordance with a preferred embodiment of the present invention, a method for generating colored images of at least one of a plurality of colors within a light-sensitive glass sample that contains light-sensitive chemical components that acquire at least one of a plurality of colors in response to actinic radiation and subsequent heating to a temperature that causes color to appear, the method comprising:
providing pulsed laser beam source having a radiation off the range of ultraviolet spectrum;
providing a focusing device for focusing said pulsed laser beam at a predetermined focus point within the glass;
providing a displacing device for providing relative predetermined displacement between the focus point and the glass sample;
focusing the laser beam to a target location within the glass;
irradiating a plurality of pulses of the pulsed laser beam focused in the target location within the glass sample so as to generate a zone of increased opacity to the visible light at the target location and a resultant localized actinic radiation at that zone;
displacing the focus point of the laser beam and the glass sample relative to each other by the displacing device in a predetermined manner so as to produce a plurality of zones of increased opacity that form an image; and
heating of the sample to a temperature that causes color to appear at the zones of increased opacity.
Furthermore, in accordance with another preferred embodiment of the present invention, the method further comprises performing, after a first color was obtained at the zones of increased opacity at least one cycle of the following steps:
irradiating the pulsed radiation by focusing the laser beam within the sample in said zones of increased opacity to the visible light; and
performing further heating of the sample to a temperature that causes another color to appear at the zones of increased opacity.
Furthermore, in accordance with another preferred embodiment of the present invention, said further heating comprises heating the glass sample to a temperature between the transformation point and the point of glass softening.
Furthermore, in accordance with another preferred embodiment of the present invention, said repeated pulsed radiation is concurrent with additional irradiation generated from a second pulsed laser beam, or from an ultraviolet lamp.
Furthermore, in accordance with another preferred embodiment of the present invention, said irradiating a plurality of pulses of the pulsed laser or repeating pulsed radiation is performed during the heating of the sample in a temperature range of 150-550xc2x0 C.
Furthermore, in accordance with another preferred embodiment of the present invention, the laser beam power density at the target location is greater than the threshold value of the sample""s glass volume breakdown.
Furthermore, in accordance with another preferred embodiment of the present invention, the pulse duration of the pulsed laser radiation is shorter than 10xe2x88x926 seconds.
Furthermore, in accordance with another preferred embodiment of the present invention, the relative displacement of the laser beam focus point and the glass sample is carried out in two dimensions.
Furthermore, in accordance with another preferred embodiment of the present invention, the relative displacement of the laser beam focus point and the glass sample is carried out in three dimensions.
Furthermore, in accordance with another preferred embodiment of the present invention, the irradiation of the pulsed laser beam focused in the target location within the glass sample is concurrent with localized heating of the irradiated zone to temperatures beyond the temperature of glass transformation point.
Furthermore, in accordance with another preferred embodiment of the present invention, the heating is performed in two stages, the first stage performed at a temperature between the transformation point of the glass sample and the glass softening point, and the second stage performed at a temperature which is by 50-120xc2x0 C. higher than that of the first stage.
Furthermore, in accordance with another preferred embodiment of the present invention, the power density of the radiation of the pulsed laser is different for at least two target locations within the glass sample.
Furthermore, in accordance with another preferred embodiment of the present invention, the light sensitive glass sample contains by mass % up to 0.25 of one or more light sensitive metals selected from Ag and Cu.
Furthermore, in accordance with another preferred embodiment of the present invention, the light sensitive glass sample contains by mass % up to 0.8 of Au and up to 0,015 Pd.
Furthermore, in accordance with another preferred embodiment of the present invention, the light sensitive glass sample contains by mass % a rare-earth element oxides selected from Sm, Tb, Pr, Eu and ceric oxide in amount: 0.01-0.03 of ceric oxide and 0.01-0.02 of others, but not more than 0.2 all together.
Furthermore, in accordance with another preferred embodiment of the present invention, the light-sensitive glass sample contains 0.01-1.2% of Sb2O3 or 0.01-1.2% of SnO, or both, not exceeding in total 2.3%.
Furthermore, in accordance with another preferred embodiment of the present invention, the light-sensitive glass sample alkaline-silicate glass and is mainly composed of the following components by mass %: 10-22 R2O; 0-18 ZnO,0-11 Al2O3; 0-9 (BeO, MgO, CaO); 0-5 B2O3; 0-12 (BaO, SrO); 0-5CdO; 0-13 (F, Br, Cl, J), SiO2 greater than 55.
Furthermore, in accordance with another preferred embodiment of the present invention, the ratio between the mass percentage of alkali oxides and the total mass percentage of halogens is in the range of 1.2-9.1.
Furthermore, in accordance with another preferred embodiment of the present invention, there is provided a method for generating colored images of at least two of a plurality of colors within a light-sensitive glass sample that contains light-sensitive chemical components that acquire at least one of a plurality of colors in response to actinic radiation and subsequent heating to a temperature that causes color to appear, the method comprising:
providing pulsed laser beam source having a radiation off the range of ultraviolet spectrum;
providing a focusing device for focusing said pulsed laser beam at a predetermined focus point within the glass;
providing a displacing device for providing relative predetermined displacement between the focus point and the glass sample;
focusing the laser beam to a target location within the glass;
irradiating a plurality of pulses of the pulsed laser beam focused in the target location within the glass sample so as to generate a zone of increased opacity to the visible light at the target location and a resultant localized actinic radiation at that zone;
displacing the focus point of the laser beam and the glass sample relative to each other by the displacing device in a predetermined manner so as to produce a plurality of zones of increased opacity that form an image;
heating of the sample to a temperature that causes color to appear at the zones of increased opacity; and
performing at least one cycle of the following steps:
irradiating the pulsed radiation by focusing the laser beam within the sample in said zones of increased opacity to the visible light;
heating of the sample to a temperature that causes another color to appear at the zones of increased opacity.
Furthermore, in accordance with another preferred embodiment of the present invention, there is provided an apparatus for generating colored images of at least one of a plurality of colors within a light-sensitive glass sample that contains light-sensitive chemical components that acquire at least one of a plurality of colors in response to actinic radiation and subsequent heating to a temperature that causes color to appear, the apparatus comprising:
pulsed laser beam source having a radiation off the range of ultraviolet spectrum;
focusing device for focusing said pulsed laser beam at a predetermined focus point within the glass;
displacing device for providing relative predetermined displacement between the focus point and the glass sample; and
controller for controlling and activating the pulsed laser beam source, the displacing device and the timing and synchronization of both.
Furthermore, in accordance with another preferred embodiment of the present invention, the pulsed laser beam source generates pulsed radiation whose duration is shorter than 10xe2x88x926 sec.
Furthermore, in accordance with another preferred embodiment of the present invention, the pulsed laser beam source generates power density in the focus point that is higher than the threshold value of the glass volume breakdown.
Furthermore, in accordance with another preferred embodiment of the present invention, the displacing device provides two dimensional relative displacement.
Furthermore, in accordance with another preferred embodiment of the present invention, the displacing device provides three dimensional relative displacement.
Furthermore, in accordance with another preferred embodiment of the present invention, the controller comprises a computer.
Furthermore, in accordance with another preferred embodiment of the present invention, the apparatus is further provided with a heater for heating the light-sensitive glass sample.
Furthermore, in accordance with another preferred embodiment of the present invention, the heater is adapted to heat the light-sensitive glass sample to temperatures in the range 150-550xc2x0 C.
Furthermore, in accordance with another preferred embodiment of the present invention, the heater comprises a furnace.
Furthermore, in accordance with another preferred embodiment of the present invention, the apparatus is further provided with dispositioning device for dispositioning the glass sample into and out of the furnace.
Furthermore, in accordance with another preferred embodiment of the present invention, the apparatus is further provided with an additional pulsed laser beam source or an ultraviolet lamp.
Furthermore, in accordance with another preferred embodiment of the present invention, said additional pulsed laser beam source is adapted to irradiate actinic radiation.
Furthermore, in accordance with another preferred embodiment of the present invention, the controller sets the laser beam power control device to generate different power densities in at least two different zones of increased opacity.
Finally, in accordance with another preferred embodiment of the present invention, there is provided an apparatus for generating colored images of at least one of a plurality of colors within a light-sensitive glass sample that contains light-sensitive chemical components that acquire at least one of a multiplicity of colors in response to actinic radiation and subsequent heating to a temperature that causes color to appear, the apparatus comprising:
pulsed laser irradiating means having a radiation off the range of ultraviolet spectrum;
focusing means for focusing said pulsed laser beam at a predetermined focus point within the glass;
displacing means for providing relative predetermined displacement between the focus point and the glass sample; and
controlling means for controlling and activating the pulsed laser beam source, the displacing device and the timing and synchronization of both.